Application of intelligent packaging for meat products: A systematic review

Abstract Background Today, in response to consumer demand and market trends, the development of new packaging with better performance such as intelligent packaging has become more important. This packaging system is able to perform intelligent functions to increase shelf life, increase safety and improve product quality. Objectives Recently, various types of packaging systems are available for meat products, especially cooked, fresh and processed meats. But because meat products are very perishable, monitoring their quality and safety in the supply chain is very important. This systematic article briefly reviews some of the recent data about the application of intelligent packaging in meat products. Methods The search was conducted in Google Scholar, Science Direct, Elsevier, Springer, Scopus, and PubMed, from April 1996 to April 2021 using a different combination of the following keyword: intelligent packaging, and meat. Results The results showed that the intelligent packaging presents several benefits compared to traditional packaging (e.g., antimicrobial, antioxidant, and shelf life extension) at the industrial processing level. Thus, these systems have been applied to improve the shelf life and textural properties of meat and meat products. Conclusions It is necessary to control the number of intelligent compounds that are included in the packaging as they clearly influence the quality and nutritional properties as well as the final cost of the food products.

from environmental factors such as moisture, light, oxygen, microorganisms, dust and mechanical stress. Due to the growing demand of consumers for foods that are minimally processed and ready to eat, as well as due to the globalisation of the food industry, it is necessary to maintain the freshness and optimal quality of food at long times, and this leads to increasing growth tendency to novel packaging (Kerry et al. 2006).
Traditional packaging of fresh meat is done to prevent contamination, delay spoilage of the product, and allow the activity of some enzymes to improve the tenderness of meat texture, reduce weight loss, and ensure the formation of oxymyoglobin pigment (instead of metmyoglobin) for the bright red colour (Panea et al., 2014). However, today, with the advancement of technology and increasing demand from consumers and industry, traditional packaging methods are not able to provide meat products that have longer shelf life, and are safer and healthier, easier to consume, in line with the environment, and reduce food waste (Ahmed et al., 2018). In response to these challenges, a new generation of packaging called intelligent packaging has been introduced to the market (Choi et al., 2014).
Intelligent packaging is one of the new packaging technologies in recent years for various foods, including meat and meat products. Intelligent packaging informs the consumer about the status of the food by understanding some of the characteristics of the food in the package or the characteristics of the environment (Panea et al., 2014). The most important intelligent packaging tools are sensors and indicators.
Intelligent packaging systems can detect and warn of product quality changes during storage. Sensors and detectors and radio frequency detection systems (RFID) are the tools used in intelligent packaging (Kerry et al. 2006).
However, there is a lack of an overview that summarises the characteristics of meat products packed in intelligent packaging. Therefore, the purpose of this study is to review the application of intelligent packaging in the meat industry such as red meat, poultry, chicken, fish and processed meat from 1996 to 2021. Moreover, current challenges in intelligent packaging were identified that can boost their technological characteristics.

Gas sensors
Gas sensors determine the gases of the space of packages and can quickly and cheaply determine the quality of the meat product (Kerry et al., 2006). Therefore, intelligent packages equipped with gas sensors have been designed. Visual chemical sensors are among these gas sensors that are able to detect the onset of spoilage by sensing gases resulting from microbial spoilage such as hydrogen sulphide (H 2 S) or carbon dioxide (CO 2 ) (in red meats) or volatile amines (in fishes) in the packaged space of meat products (Pereira et al., 2021). These gases are important to be monitored during packaging due to, for example, H 2 S, and volatile amines are produced during meat spoilage by microorganisms (Casaburi et al., 2015). The response of gas sensors correlates with bacterial growth patterns in meat samples, thus enabling 'real-time' monitoring of spoilage in different types of meat (Pacquit et al., 2006).
In visual chemical sensors, for example, pH-sensitive sensors based on the fluorescence system can be used in conjunction with the sensors. Oxygen sensors based on fluorescence are another types of gas sensors, which have been used to measure gases in the headspace of meat products (Ahmed et al., 2018).

Biosensors
Rapid, accurate and online understanding is a requirement for on-site analysis of contaminants, determination and detection of pathogens and control of food quality parameters after processing. In general, a biosensor is a compact analyser that detects, records, and transmits information about biochemical reactions (Badihi-Mossberg et al., 2007). This intelligent device has two primary components: a bioreceptor that detects target analytes and a transducer that converts biochemical signals into measurable electrical responses (Yam et al. 2005). A bioreceptor is an organic or biological substance, such as an enzyme, antigen, microbe, hormone or nucleic acid (Biji et al., 2015).
The transducer, based on the measured parameters, can exist in different forms such as electrochemical, optical, acoustic (Senturk et al., 2018).

Integrity indicators
Integrity indicator is a type of detector that is used to determine the breakdown of packages, and show the qualitative information related to packaging in the form of colour changes. The damage and of leakage in the packages is one of the most common damages to packages containing meat products, which can be detected by the above-mentioned indicators. Most of the indicators that detect leakage in the package are in fact detectors that show the presence of oxygen in the package through a leak. In these packages usually, the increase in the amount of oxygen can indicate damage and leakage in the package. In fact, oxygen enters the package through the orifice, so visual oxygen detectors are used (Ahmed et al., 2018).

Freshness indicators
Freshness indicators provide direct quality information about the product as a result of microbial growth or chemical changes in the food product. Microbiological quality may be detected by reactions between encapsulated markers and microbial growth metabolites. Changes in the concentrations of organic acids such as n-butyrate, L-lactic acid, D-lactate and acetic acid during storage as potential metabolites for a number of meat products provide information about the freshness of product. These microbial metabolites are produced during growth, activity and metabolism of microorganisms. They have an effect on the freshness indicators of meat products (Casaburi et al., 2015). Colourbased pH sensing is used as indicators of these microbial metabolites (Rokka et al., 2004).

Time temperature indicators (TTI)
Temperature is usually the most important environmental factor that like microbial growth, affects the kinetics of physical and chemical degradation in food products. Time-temperature indicators (TTIs) are very useful in the food industry because they can alert the consumer when food is exposed to inappropriate temperatures. TTIs are usually small self-adhesive labels that are affixed to shipping containers or single packages. These labels have visual indications of the temperature background during distribution and storage, which are especially useful for warning of unsuitable temperatures for refrigerated or frozen food products. These detectors are also used to estimate the remaining shelf life of perishable products. All of the commercially available TTIs have the potential to be used in meat products (Vaikousi et al., 2009).

Tag/barcodes
A barcode is a machine-readable storage database that operates on the optical phenomenon of bars of regular width and thickness. If pathogenic bacteria grow inside the package during the storage, it can be detected by the bar code and as a result, the colour changes and the bar code becomes unreadable (Kerry et al., 2006).

Radio frequency detection (RFID)
Radio frequency detection systems are one of the most diverse technologies for automatic detection or identification. RFID systems have many advantages in the production, warehousing, distribution and retail chains of meat products. The reduced maintenance costs, safety and improvement of the quality of the product and prevention of the return of the product are some benefits of RFID systems (Kerry et al., 2006).

Need for intelligent packaging of meat products
Meat is one of the most perishable food groups, and the correct packaging, in addition to increasing the shelf life, plays an important role in reducing waste and increasing the level of public health by reducing pollution caused by the use of unsanitary and inappropriate products. Meat spoilage is mainly caused by microbial degradation and lipid oxidation due to its high water activity (a w ) and fat content. Spoilage of meat products can lead to quality loss such as colour change, off-flavour, loss of crispness, and change in pH, which ultimately causes in consumer rejection and economic losses (Ahmed et al., 2018;Wojnowski et al., 2017).
Off-odour is one of the key indicators of meat spoilage. These odours are generally attributed to the accumulation of volatile compounds in the packaging headspace, particularly sulphur-containing compounds, biogenic amines and other low-molecular-weight VOCs, which are mainly caused by microbial activity on proteins, amino acids, and carbohydrate substrates (Luo et al., 2022). Br. thermosphacta is one of the important bacterial species responsible for off-odour and S. putrefaciens is known to produce hydrogen sulphide during meat spoilage (Casaburi et al., 2015).
The primary method for detecting meat spoilage is microbiological testing through the total count of bacteria and/or microbial species causing spoilage, including Acinetobacter spp., Brochothrix thermosphacta, Enterobacteriaceae, Lactobacillus spp., Pseudomonas spp.
and Shewanella (Wojnowski et al., 2017). Sensory analyses based on colour change, off-odour and sliminess are common (Ahmed et al., 2018). These methods are time-consuming, laborious and require special expertise. Therefore, the development of new rapid techniques that can reflect meat quality in real-time and detect its spoilage is valuable for the meat industry. Gas chromatography is the most common method to determine the volatile compounds from meat spoilage. This technique is relatively expensive and requires instrumental expertise (Luo et al., 2022).
The packaging of meat products is to prevent contamination, delay spoilage and allow some enzyme activities to improve softness, dehy-

Search strategy
In this systematic review, the specialised databases, namely, Google

Data handling, analyses and extraction
The inclusion criteria for handling of studies were outlined according to PRISMA guidelines and used were the following: (1)

Study identification and selection
Of the 300 full texts reviewed, 138 relevant articles were identified, which was in agreement with our inclusion and exclusion criteria. The selected articles were grouped into intelligent packaging and nanoparticles in meat products. The complete process is shown in Figure 2, which is based on a PRISMA flow chart.

Intelligent packaging
Types of intelligent packaging and commercial applications for meat products are summarised in Table 2. The results of applications of intel-ligent packaging in meat products of selected articles and their main results are presented in Table 3. In total, 84 articles were identified and characterised the effects of intelligent packaging for meat products.
According to the results, intelligent packaging described the microbial quality and is an effective spoilage indicator by evaluating their reaction to the metabolites produced during the growth of microorganisms or during chemical changes within the meat products.

DISCUSSION
In industrialised countries, food companies make large investments in the use of novel packaging technologies, and it is believed that if the packaging is suitable in different ways and can provide satisfy the consumers, will lead to more product sales and faster return on investment with appropriate profits (Ahmed et al., 2018).
Intelligent packaging systems are systems that can detect, signal and warn of food product quality changes during storage. Sensors and indicators [e.g., integrity detectors, time-temperature (TTI) detectors and radio frequency detection (RFID) systems] can be used in intelligent packaging (Kerry et al., 2006). In order to develop the commercial application of these technologies, the knowledge and awareness of industry about their benefits, increase the efficiency of these technologies, paying attention to the economic aspects of their use and increase consumer acceptance. In this article, the results of some

Indicator Food product Function References
Chilled boneless chicken breast Quality control Brizio and Prentice (2014) Atmosphere packed gilthead seabream fillets UV activatable photochemical TTI Tsironi et al. (2011) Chilled vacuum-packed grouper fillets Some studies for monitoring pork and buffalo meat freshness were published (Choi et al., 2017;Li et al., 2014;Shukla et al., 2015) with a colourimetric sensor sensitive to TVB-N released during meat storage.
A much simpler sensor was developed by Pablos et al. (2015) to detect beef freshness. These sensors were based on colour changes, when in contact with the atmosphere inside the package.
Similar findings have been reported in the literature in regards to monitoring raw and processed meat (Kerry et al., 2006) as a tool to reduce their wastes and prolonging the shelf life of products.
So far, various nanoparticles have been used in the intelligent packaging of meat and meat products. Many studies have been done on the antimicrobial effect of gold and silver nanoparticles on various microorganisms. Silver nanoparticles also reduced the microbial load of beef packaged under the modified atmosphere. Morsy et al. (2014) reported edible films made from pullulan incorporated with essential oils and AgNPs can maintain the quality of processed meat and poultry products. Similarly, commercial films coated with AgNPs could be to increase the shelf life of Turkey meat (Deus et al., 2017).
Continuous research seems to be needed to access the benefits and capabilities of intelligent packaging for meat and meat products.
The scope of this research may be more appropriate in cases such as modelling of interactions between foods and microorganisms and their metabolites in different storage conditions, the relationship between the detection of spoilage and the sensory quality of food, suitable sensors and detectors, the behaviours and characteristics of tools used for intelligent packaging in different parts of the production, warehousing and distribution chain, as well as a more complete understanding of the sensitivities and reliability of intelligent packaging and their tools (Ahmed et al., 2018, Kerry et al., 2006. The potential benefits of intelligent packaging for meat and muscle products are varied. Paying attention to the positive effects of this type of packaging on the quality, safety and health of food in different stages, we must also pay attention to its economic and marketing aspects (Panea et al., 2014).
The increasing consumer information and awareness of consumers and their demands are among the factors that force manufacturers and researchers to innovate, develop and optimise modern packaging technologies (Ahmed et al., 2018). Different forms of intelligent packaging such as the use of oxygen sensors, freshness and time-temperature indicators are the answers that researchers and scientists have developed these demands. If the necessary coordination between efficiency and usefulness is established with the economic aspects of the use of intelligent packaging, in the future, the use of these new technologies for packaging various foods, including meat and meat products, will be inevitable (Kerry et al., 2006). be paid attention to its economic and marketing aspects. The aware-ness of consumers is force manufacturers and researchers to innovate and develop and optimise modern packaging technologies. Various forms of intelligent packaging, such as oxygen sensors, freshness and spoilage indicators and time-temperature detectors, are answers that researchers and scientists have devised to meet the aforementioned demands. If the necessary coordination between efficiency and usefulness is established with the economic aspects of the use of intelligent packaging, it will be inevitable to use these technologies in the future.

CONCLUSIONS
In this article, the results of some research and articles related to new technologies and their applications for the packaging of meat and meat products are presented. Monitoring the quality and spoilage of fresh meat products is essential in order to reduce the incidence of foodborne illness and reduce the production of meat waste throughout the supply chain. However, traditional packaging systems are able to provide few services in the field of supply chain monitoring. But new intelligent packaging systems with the aim of monitoring the quality of packaged meat or its environment are advancing towards providing innovative solutions in the industry of production and supply of meat products. So, a variety of commercial freshness, temperaturetime, integrity and radio frequency detectors with intelligent concepts, in order to improve storage conditions and reduce waste of fresh and safer meat products, have been introduced to the food market. However, each of these methods has advantages and disadvantages, which affect the performance and efficiency of the system. Therefore, it is necessary to control the number of intelligent compounds that are included in the packaging as they clearly influence the quality and nutritional properties as well as the final cost of the food products.

ETHICS STATEMENT
In this manuscript, all the ethical principles related to writing a review article, including maintaining trustworthiness and avoiding plagiarism, have been observed.